Like a cake, the ocean has different layers—each with its own characteristics. (No icing, though.) The surface layer receives the most sunlight, allowing photosynthetic organisms like phytoplankton to convert sunlight to energy. The twilight zone receives only faint, filtered sunlight, allowing no photosynthetic organisms to survive. Many animals have adapted to the near-darkness with large eyes and counterillumination. The deep ocean (or aphotic zone) gets no sunlight at all; animals create their own bioluminescent light and have light-sensitive eyes to sense the bioluminescent light of other animals. Drop from the surface to the deep in this to-scale image and learn more about the deep sea in our overview.